docs: rewrite README with structured overview and quick start guide

Replaces the minimal project description with a comprehensive README
including a component overview table, quick start instructions, common
Ansible operations, and links to detailed documentation. Aligns with
Red Panda Approval™ standards.

ansible/grafana_mcp/deploy.yml

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+---
+# Grafana MCP Server - Docker Compose deployment on Miranda
+#
+# Grafana itself runs inside the PPLG stack on Prospero (see docs/pplg.md).
+# This playbook deploys the Grafana MCP server container on Miranda, which
+# connects back to Grafana on Prospero via the internal Incus network.
+#
+# Prerequisites:
+#   - PPLG stack deployed on Prospero (ansible-playbook pplg/deploy.yml)
+#   - Grafana service account token in vault (vault_grafana_service_account_token)
+#   - Docker installed on the target host (ansible-playbook docker/deploy.yml)
+#
+# See also: docs/grafana_mcp.md
+
+- name: Deploy Grafana MCP Server with Docker Compose
+  hosts: ubuntu
+  become: true
+  vars:
+    required_service: grafana_mcp
+  tasks:
+  - name: Check if host has grafana_mcp service
+    ansible.builtin.set_fact:
+      has_grafana_mcp_service: "{{ required_service in services | default([]) }}"
+
+  - name: Skip hosts without grafana_mcp service
+    ansible.builtin.meta: end_host
+    when: not has_grafana_mcp_service
+
+  - name: Verify Grafana is reachable on PPLG host
+    ansible.builtin.uri:
+      url: "http://{{grafana_mcp_grafana_host}}:{{grafana_mcp_grafana_port}}/api/health"
+      method: GET
+      status_code: 200
+    register: grafana_health
+    retries: 3
+    delay: 5
+
+  - name: Create grafana_mcp group
+    ansible.builtin.group:
+      name: "{{grafana_mcp_group}}"
+
+  - name: Create grafana_mcp user
+    ansible.builtin.user:
+      name: "{{grafana_mcp_user}}"
+      comment: "{{grafana_mcp_user}}"
+      group: "{{grafana_mcp_group}}"
+      system: true
+
+  - name: Add group grafana_mcp to Ansible remote_user
+    ansible.builtin.user:
+      name: "{{remote_user}}"
+      groups: "{{grafana_mcp_group}}"
+      append: true
+
+  - name: Create grafana_mcp directory
+    ansible.builtin.file:
+      path: "{{grafana_mcp_directory}}"
+      owner: "{{grafana_mcp_user}}"
+      group: "{{grafana_mcp_group}}"
+      state: directory
+      mode: '750'
+
+  - name: Template docker-compose file
+    ansible.builtin.template:
+      src: docker-compose.yml.j2
+      dest: "{{grafana_mcp_directory}}/docker-compose.yml"
+      owner: "{{grafana_mcp_user}}"
+      group: "{{grafana_mcp_group}}"
+      mode: '550'
+
+  - name: Reset SSH connection to apply group changes
+    meta: reset_connection
+
+  - name: Start Grafana MCP service
+    community.docker.docker_compose_v2:
+      project_src: "{{grafana_mcp_directory}}"
+      state: present
+      pull: always
+
+  - name: Verify Grafana MCP container is responding
+    ansible.builtin.uri:
+      url: "http://localhost:{{grafana_mcp_port}}/mcp"
+      method: GET
+      status_code: [200, 405]
+    register: grafana_mcp_health
+    retries: 5
+    delay: 5
+    ignore_errors: true
+
+  - name: Report Grafana MCP health status
+    ansible.builtin.debug:
+      msg: "Grafana MCP container is {{ 'responding' if not grafana_mcp_health.failed else 'not responding - check docker logs grafana-mcp' }}"

ansible/grafana_mcp/docker-compose.yml.j2

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+services:
+  grafana-mcp:
+    image: mcp/grafana:latest
+    pull_policy: always
+    container_name: grafana-mcp
+    restart: unless-stopped
+    ports:
+      - "{{grafana_mcp_port}}:8000"
+    environment:
+      - GRAFANA_URL=http://{{grafana_mcp_grafana_host}}:{{grafana_mcp_grafana_port}}
+      - GRAFANA_SERVICE_ACCOUNT_TOKEN={{grafana_service_account_token}}
+    command: ["--transport", "streamable-http", "--address", "0.0.0.0:8000", "--tls-skip-verify"]
+    logging:
+      driver: syslog
+      options:
+        syslog-address: "tcp://127.0.0.1:{{grafana_mcp_syslog_port}}"
+        syslog-format: "{{syslog_format}}"
+        tag: "grafana-mcp"